Jet sand blasting of bent tubes or rods

ABSTRACT

U-shaped rods or tubes are sandblasted in that first one leg is passed through an annular duct having radially inwardly directed blasting nozzles; this duct is thereafter pivoted so that blasting follows the contour of the curved portion of such a rod or tube, and the other leg thereof is blasted upon retraction. The rod or tube is moved by means of roller tracks having lateral guide rollers to obtain exact positioning during sandblasting of the legs.

United States Patent 1 Kollbach [4 1 May 13, 1975 JET SAND BLASTING OFBENT TUBES OR RODS [75] Inventor: Wilhelm Kollbach,

Erkrath-Unterbach, Germany [22] Filed: July 30, 1974 [2]] Appl. No.:493,090

[30] Foreign Application Priority Data [56] References Cited UNITEDSTATES PATENTS 2,451,635 10/1948 Schratt 51/14 Wallace Curtiss PrimaryExaminerDonald G. Kelly Attorney, Agent, or FirmRalf H. Siegemund [57]ABSTRACT U-shaped rods or tubes are sandblasted in that first one leg ispassed through an annular duct having radially inwardly directedblasting nozzles; this duct is thereafter pivoted so that blastingfollows the contour of the curved portion of such a rod or tube, and theJuly 30, Germany other leg thereof is blasted upon retractior The rod ortube is moved by means of roller track's having lat- [52] U.S. Cl. 51/14id r llers to obtain exact positioning during [51] Int. Cl. B24c 3/12;B240 3/32 Sandblasting f the l [58] Field of Search 51/14, 8 R, 290,319-321 4 Claims, 2 Drawing Figures JET SAND BLASTING OF BENT TUBES ORRODS BACKGROUND OF THE INVENTION The present invention relates tosandblasting of tubes or rods bent in hairpin fashion, i.e., havingU-shaped configuration.

Sandblasting straight tubes and rods is generally known and practicedwith advantage. However, difficulties arise when the tubes are curved,and in the past the usual procedure was that the tubes were blasted whenstill straight, and they were bent subsequently. That method, however,resulted in changes in the surface texture of the tubes due to thebending, and the surface could no longer be treated adequately to obtainthe desired degree of uniformity in surface texture.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide an apparatus and device for providing blasting jets foruniformly and transitionless sandblasting curved and bent pipes, tubesor rods, particularly when even bent in hairpin fashion.

In accordance with the present invention, it is suggested to provide ablasting chamber with a pivotable annular duct and radially inwardlydirected blasting nozzles; roller tracks run the tubes or rods to besandblasted into the chamber, whereby one leg of such a tube or rod isguided through the annular duct followed by pivoting the latter on avertical axis for blasting the curved portion of the tube or rod. Theother leg of the tube or rod is blasted upon retraction of the tube orrod from the chamber by means of the nozzles of the same annulus.Alternatively, a second annulus with blasting nozzles treated thissecond leg in parallel with the first one.

The guiding of a rod or tube to be sandblasted is preferably carried outby vertically disposed rollers flanking the roller tracks. These guiderollers could engage the bent tube or pipe on the outside as to bothlegs, but guiding one leg from both sides may also be used.

DESCRIPTION OF THE DRAWINGS While the specification concludes withclaims particularly pointing out and distinctly claiming the subjectmatter which is regarded as the invention, it is believed that theinvention, the objects and features of the invention and furtherobjects, features and advantages thereof will be better understood fromthe following description taken in connection with the accompanyingdrawings in which:

FIG. 1 is a top view of the equipment in accordance with the preferredembodiment of the invention; and

FIG. 2 shows the pivotal blasting nozzle, on an enlarged scale, beingpart of the equipment shown in FIG. 1.

Proceeding now to the detailed description of the drawing, theillustrated equipment includes a roller track with horizontally arrangedreversible rollers l. The drive for these rollers is not illustrated andis conventional. The track is flanked on both sides by verticallyarranged rollers 2 for guiding a hairpin bent or U- shaped tube in aparticular orientation on the roller track proper.

The sandblasting equipment is contained in a casing 3, defining thesandblasting chamber. This chamber has an entrance adjacent the end ofthe track with rollers l and an exit located opposite the entrance.Entrance and exit of the blasting chamber are sealed to some extent bycurtains 4 or the like to prevent escape of sand but permitting passageof the pipe.

The casing 3 contains a pivot arm 9 carrying a ring or annular duct 7with a gap, and nozzles 8 project radially inwardly from duct 7.Respectively, two of the nozzles project in diagonally oppositedisposition towards each other. Sand under pressure is fed, for example,through a journalled hollow shaft 11 from a suitable supply and pressuresource and passes into the annular duct 7 for distribution to nozzles 8.

The pivot arm with annulus 7 and nozzles 8 is pivoted by means of areversible drive, covering for each pivot motion. However, for reasonsof simplicity, the return motion for the pivot arm may not cover thesame 180 in reverse motion, but may complete one turn as will be shownshortly.

The roller track 1 could also be termed the feeder track for theapparatus and blasting equipment. A second roller track 5 is provided onthe other side of the blasting equipment. Adjacent to the exit of theblasting chamber in casing 3, track 5 could also be termed the controltrack. Lateral guide rollers are also provided here, and a stop 6 isprovided at the end of that track 5. Upon engagement of the stop 6 by atube contacts are actuated to control the roller tracks and other operations as will be explained shortly.

In operation a bent tube section 10 is placed onto roller track 1 in theillustrated position, i.e., with the legs extending towards the blastingchamber. The guide rollers 2 maintain that orientation. The pivot arm 9holds the nozzle ring 7 to one side, and as the tube 10 enters theblasting chamber, one leg of the tube traverses the ring and issandblasted as shown in FIG. 2.

As the tube 10 passes through the blasting chamber, the front ends ofthe two legs of U-shaped tube 10 will be engaged by the rollers 5 of thesecond track which cause the tube to moved until the front ends of thelegs abut stop 6. The stop 6 has disposition so that now the curvedportion of tube 10 is situated entirely in the blasting chamber wherebyparticularly the pivot axis of arm 9 traverses the center of curvatureof the bent tube portion at the bottom of the U.

Upon abutment of the tube against stop 6, the roller tracks are stoppedand the drive for pivot arm 9 is set into motion to turn the arm by 180.Upon completion of that pivot motion, the pivot arm stops, and tracks 1and 5 are again turned on, but in the reverse, and tube 10 is returnedwhereby now the other leg of the tube passes through the nozzle ring 7until withdrawn from the chamber.

It can readily be seen that upon rapid action control and proportioningof the pivot and roller speeds, all portions of the tube can be made topass through the nozzle ring at the same relative speed to obtainuniform blasting treatment throughout.

After the tube 10 so treated has been withdrawn, the pivot arm 9 maycontinue its pivot motion to complete a full turn, so as to assume theinitial disposition of readiness for the next tube 10 to be sandblasted.Alternatively, the next tube 10 can be treated in the reverse order asto its legs, and the bent or curved portion can be sandblasted on thereverse pivot of annulus 7 on arm 9.

In the illustrated equipment a single nozzle ring is used to obtain theblasting treatment in a reversing process as far as the tube movement onthe rollers is concerned. Alternatively, one could use a second ring,which does not have to be pivotal, for blasting the second leg of thetube, and after the pivoting has been completed for blasting the curvedportion, stop 6 is golded away and track 5 continues in the samedirection to move the tube out of the blasting chamber and onto furtherconveying equipment. It can be seen that the gap in the nozzle ring orrings have to be provided for only in this case; an uninterruptedannulus can be used when the tube is reversed as was described first.Simply pivoting the annular duct 7 with nozzles 8 will suffice, if thecurved or bent tube or rod portion follows a circular arc; the center ofthe annulus simply follows the bent axis of the tube during pivoting.However, the invention is also applicable to other contours of tube orrod curvature. In such cases one has to provide additionally for lateraldisplacement of the pivot. Also, additional roller track movement mayaid in accurately following the contour of the curved tube portion.

The invention is not limited to the embodiments described above, but allchanges and modifications thereof not constituting departures from thespirit and scope of the invention are intended to be included.

I claim:

1. Apparatus for sandblasting hairpin bent tubes or rods comprising: i

a blasting chamber with aligned entrance and exit;

a first roller track disposed for moving such tubes or 4% v a rods toand into the blasting chamber through the entrance; I y it a secondroller track disposed for moving the tubes or rods from the blastingchamber when emerging from the exit;

an annular duct with radially inwardly directed blasting nozzlesdisposed in the blasting chamber so that'z I one leg of a bent tube orrod, when moved into the Y i chamber by the first roller track,traverses the-annular duct for sandblasting through jets as ejected 1from the nozzles; and I I g means for pivotally mounting the annularductformoving the annularduct with nozzles along the bent axis of thecurved portion of the tube or rod for sandblasting the saidcurvedportion. 2. Apparatus as in claim 1, wherein the rollers of the 7 tracksare, reversible for blasting the other leg upon reversal of the rollersof the tracks after pivotingof the,

annular duct, as the other leg passes through the annu- I lar ductduring said reversal.

3. Apparatus as in claim 1, the roller tracks having lateral guides forproviding for guided motion of the. tube throughthe annular duct.

1. Apparatus for sandblasting hairpin bent tubes or rods comprising: ablasting chamber with aligned entrance and exit; a first roller trackdisposed for moving such tubes or rods to and into the blasting chamberthrough the entrance; a second roller track disposed for moving thetubes or rods from the blasting chamber when emerging from the exit; anannular duct with radially inwardly directed blasting nozzles disposedin the blasting chamber so that one leg of a bent tube or rod, whenmoved into the chamber by the first roller track, traverses the annularduct for sandblasting through jets as ejected from the nozzles; andmeans for pivotally mounting the annular duct for moving the annularduct with nozzles along the bent axis of the curved portion of the tubeor rod for sandblasting the said curved portion.
 2. Apparatus as inclaim 1, wherein the rollers of the tracks are reversible for blastingthe other leg upon reversal of the rollers of the tracks after pivotingof the annular duct, as the other leg passes through the annular ductduring said reversal.
 3. Apparatus as in claim 1, the roller trackshaving lateral guides for providing for guided motion of the tubethrough the annular duct.
 4. Apparatus as in claim 1 and including stopmeans for the legs of the tube rod to position the center of the curvedportion in the pivot axis of the annular duct.